The present invention relates to methods and apparatus for removing contaminant substances from earth materials inclusive of soil and minerals. More particularly, the present invention relates to methods and apparatus for removing contaminant, undesirable substances from soils, minerals, clays, sediments, sludges and acquiescent slurries by energizing said slurries through electric current flow which produces volume boiling physical dislodgement of the contaminant component from the soil particular matter.
Earth materials inclusive of soils, minerals, sediments and acquiescent slurries containing earth materials may become contaminated with a wide variety of toxic and hazardous substances as a result of leaks, spills and inadequately managed landfills. Frequently, the soil or earth contaminants fall into two categories, organic materials including hydrocarbons and heavy metals. Current federal and state regulations require that these contaminants be removed from the earth materials. A wide variety of processes have been developed for this task. For example, a process such as incineration of soil can effectively destroy organic contaminants, but is expensive and may permanently alter the soil itself, and is not effective for removal of heavy metals. If the contaminant is soluble and solvent, solvent extractions can be used to remove the contaminant, however, solvent extraction is an expensive process since the solvent must be separated from both contaminants and the treated soil and reused. If the contaminant is volatile, it may be vaporized from the soil by sample heating, however, such volatile emissions are objected to by the same current federal and state regulations. Biodegradable contaminants may be removed by microbial action, but such a process is a rather slow process and must be monitored carefully to maintain large concentrations of effective microbes.
It is well known and documented that there are many sites in the United States and the world where major hydrocarbon and/or toxic waste spills or dumping have occurred that contaminate an area both on the surface and below ground at the site. Many such sites are associated with former or existing petroleum or petrochemical processing plants, chemical manufacturing facilities including those making insecticides and other toxic chemical substances, or sites where waste materials are intentionally or inadvertently dumped for disposal.
Such sites have earth materials that are contaminated either at the earth's surface or subsurface or both. Such contamination poses hazards to people, animals and plant life exposed to the materials at the surface, or even more insidious and dangerous, is the long-term hazards to drinking water supplies because of percolation through the earth by leaching of ground water out of the immediate site. In addition, oil spills along coast lines, although not frequent, can cause severe damage to marine and wildlife in the effective area, damage water resources and cause severe economic loss in the effected area. Cleanup methods are exceedingly expensive and cumbersome, time consuming, and result in large quantities of polluted materials, usually contaminated earth materials that must be disposed of at yet another geographic location.
Isolation and removal of these contaminated earth materials to another remote location for disposal and/or treatment involves considerable expense. Such removal necessarily involves containment and often the containerized materials are stored for long periods of time or never processed due to the difficulty and/or expense associated with processing. Frequently, contaminated earth materials must be excavated and removed in an attempt to remove all of the contaminated earth materials present, said excavation requires a substantial task, frequently within cities wherein, for example, established gasoline tanks have existed for years. Such excavated and removed earth materials often involve hundreds of tons of materials which are shipped in suitable protective containers or secured vehicles to remote processing site or more commonly for disposal in a remote dump site.
On-site treatment of contaminated earth materials has been attempted, principally on small sites where chemical neutralization and/or removal have been attempted with limited success, or the contaminated materials are incinerated to burn the pollutant substances. However, there is considerable controversy involving incineration methods and the potential release of unburned pollutants and hazardous materials into the atmosphere. Most chemical treatment and recovery methods remain ineffective and pose intolerable expense and sometimes questionable results.
No truly satisfactory method of overall soil treatment and purification has been previously available. Generally, treatment methods have involved either incineration alone, microbial treatment, solvent extraction, vaporization or some combination thereof. These methods have not completely been satisfactory. For example, the typical incineration process requires a large incinerator to be assembled near the contaminated soil or be at some remote location. The incineration processes generally destroy much of the organic material and also result in a large volume of ash material which may still be substantially contaminated and must be secured in yet another dump site.
Microbial purification of various hydrocarbon contaminates has not proven to be totally satisfactory. While in the laboratory microbial action may be shown to be capable of detoxifying soil materials, in the field such methods are less efficient. For example, variations in soil conditions such as temperature, moisture and oxygen create a control issue hence, these, variables are essential to the process and yet difficult to achieve. Further, complete microbial detoxification of concentrated contaminants may take long periods of time and during that period of time further leaching from the dump site may occur.
Soil washing is a simple, direct approach for removal of many organic and inorganic contaminants from soil. In soil washing technology's current state of development, soil washing is most applicable to soil containing only small portions of silts and clays. These clays and silts frequently remain contaminated after washing with existing processes, and so they must be treated by other processes, or stored indefinitely in a secure landfill. The very large specific surface area of clays and silts provides the opportunity for large quantities of contaminants to become attached to the soil by a variety of mechanisms. In addition, it is difficult to apply energy directly to the very small particles to dislodge the contaminants. For these reasons, current applications of soil washing processes are to soils containing mostly coarse silt and sand.
These disadvantages of the prior art are overcome by the present invention which provides novel methods and apparatus for on-site isolation and treatment in removal of contaminant substances from the contaminated earth material, including recovery of such contaminant substances and the return of the cleansed and decontaminated earth materials to the excavation site.